Weighted drill collar



July 31, 1962 cs. H. BRUCE WEIGHTED DRILL COLLAR Filed Oct. 27, 1961 INVENTOR. GEORGE H. BRUCE.

AFR

United States Patent 3,047,313 WEIGHTED DRILL COLLAR George H. Bruce, Houston, Tex., assignor, by mesne assignments, to Jersey Production Research Company, Tulsa, Okla., a corporation of Delaware Filed Oct. 27, 1961, Ser. No. 148,268 5 Claims. (Cl. 285-47) The present invention is directed to an improved drill collar. More specifically, the invention is directed to an improved drill collar which increases the weight of a drill string in which it is arranged. In its more specific aspects, the invention is concerned with a heavy drill collar which utilizes the pendulum effect in preventing hole deviation in drilling wells with a drill string.

This application is a continuation-in-part of Serial No. 850,869 entitled, Drill Collar, and filed November 4, 1959 for George H. Bruce, and now abandoned.

The present invention may be briefly described as a drill collar for use in a drill string which comprises inner and outer spaced-apart elongated wall members. Arranged between the wall members and bondedly attached thereto are cellular reinforcing means which provide strength for the drill collar. The inner of the wall members provides an unobstructed bore for passage of fluid and tools therethrough. Means are attached to each end of the wall members for connecting the drill collar threadedly into a drill string. In the cellular reinforcing means there is arranged in the cells thereof a weighting means such as a heavy metal or a derivative thereof having a specific gravity greater than 8.0. By virtue of the drill collar in accordance with the present invention, a heavy drill collar is provided which utilizes the pendulum effect in drilling wells in a drill string having the drill collar therein.

The present invention will be further described by reference to the drawing in which the single FIGURE is an elevational view partly in section of a preferred embodiment.

The drill collar of the present invention is made up of a thin-walled outer tubular member 11 and a thin-walled inner tubular member 12. These tubes 11 and 1'2 are spaced apart and are separated by a cellular structure 13 which may be of a honeycomb type such as used in reinforcing the airfoils of high-performance aircraft. Honeycomb structure 13 is provided with passages into each cell and throughout the length of the drill collar generally indicating by the numeral 14 to allow a filler material to be placed in the honeycomb structure 13. The outer tubular member is also suitably provided with means for introducing filler material into the cellular structure. The outer tubular member 11 and the inner tubular member 12, forming the drill collar 14, have connecting means 15 and 16 attached to each end thereof for attaching the drill collar 14 into a drill string for use in drilling a well. The connecting means 15 and 16 are provided with threads 17 and 18, respectively, for threadedly connecting the drill collar 14 into a drill string for use in drilling operations. The connecting means 15 and 16 are provided with recesses 19, 20, 21, and 22 into which the wall members 11 and 12 fit such that the wall members .11 and 12 may be rigidly and fixedly attached to the connecting means 15 and 16.

The heavy metal employed as a filler in the honeycomb or cellular structure 13 is preferably lead, but other heavy metals such as mercury, tungsten, osmium, and uranium maybe used. Also the derivatives of these metals such as oxides and the like may be used such as the oxides of lead, mercury, tungsten and uranium. To illustrate the difference in weights of the several heavy metals as compared to iron or steel which usually makes up the drill collar, the specific gravity of iron is compared Cir "ice

to the specific gravities of the several heavy metals in Table I.

Certain alloys may also be used as the filler in the present invention. For example, alloys of lead may be used; woods metal, antimonial lead and plumbers solder may be employed. These alloys have specific gravities of 9.7, 11.0, and 9.4, respectively.

The device of the present invention is easily constructed and the tubular members :11 and 12 may suitably be flash welded to the connecting means 15 and 16.

In order to illustrate the present invention, a drill collar of five-inch outside diameter and two-inch inside diameter with a quarter-inch inner wall and three-eighths-inch outer wall and filled with lead will weigh about 70 pounds per foot when made of steel, which has a density of about 490 pounds per cubic foot. Lead has a density of about 700 pounds per cubic foot. The same. collar made of steel alone weighs about 56 pounds per foot; thus the dense or heavy metal provides a 25 percent increase in the weight with no increase in diameter.

The employment of sandwich or cellular or honey comb type of structure has been well developed in many years and is well known to the art. It is apparent that the cellular reinforcing means is necessarily formed of a high melting point metal which is substantially chemically inert to and is not attached by the heavy metal weighting means received in the cells in a liquid state. A collar such as described herein is therefore easy to construct and is of substantially the same strength as the conventional drill collar, but is of greater weight than the conventional drill collar. Thus, the available weight per foot may be increased without increasing the drill collar diameter. Drill collars such as in the present invention will be as strong and rigid as those currently in use which are usually formed by 'boring and turning operations from large forged steel billets. Thus, the present invention provides a drill collar which is heavier and is competitive in cost with the conventional drill collar.

Moreover, the drill collars now used in drilling opera tions to provide weight to the drill bit and to prevent borehole deviation sometimes fail to achieve this end. The drill collars, to prevent hole deviation, utilize the pendulum effect and to achieve this must be heavy and rigid. The conventional drill collars made of thick walled pipe and manufactured by boring and turning a solid steel forging have weight and rigidity from the thickness of the wall. Since borehole diameters are limited, wall thickness of the conventional drill collar is also limited. The present invention provides a means for adding additional weight to drill strings in drill collars where the diameter of the borehole is limited. Accordingly, the present invention is quite advantageous and useful in that providing additional weight and thus utilizing the pendulum effect, boreholes may be drilled straighter with less deviation than now is frequently encountered.

While specific examples of the several heavy metals and oxides thereof have been given, these examples are by way of illustration and not by way of limitation since any heavy metal or material having a specific gravity greater than 8.0 may be used as the filler material.

The nature and objects of the present invention having been completely described and illustrated, what I wish to claim as new and useful and secure by Letters Patent is:

l. A drill collar for use in a drill string which comprises inner and outer spaced apart tubular wall members, cellular reinforcing means between and bondedly attached and secured at least to said wall members throughout the length thereof, said cellular reinforcing means forming a plurality of cells in and throughout the length and width of said space with passageways in said cellular reinforcing means into each cell, the inner of said wall members providing an unobstructed bore for passage of fluid, means attached to each end of said wall members for connecting said drill collar into a drill string, and metal weighting means having a specific gravity greater than 8.0 in and filling said cells whereby a heavy drill collar and a pendulum effect to said drill string are provided, said cellular reinforcing means being formed of a high melting point metal substantially chemically inert to and unattacked by said metal weighting means received into said cells in a liquid state.

2. A drill collar in accordance with claim 1 in which the metal Weighting means is lead.

3. A drill collar in accordance with claim 1 in which the metal weighting means is mercury.

4. A drill collar in accordance with claim 1 in which the metal weighting means is an alloy of lead.

5. A drill collar in accordance with claim 1 in which the cellular reinforcing means provides a honeycomb structure.

References Cited in the file of this patent UNITED STATES PATENTS 1,712,803 Wood May 14, 1929 1,746,132 Stockes Feb. 4, 1930 2,126,075 Wright Aug. 9, 1938 2,814,462 DeJarnett Nov. 26, 1957 

